Momentarily consolidated board product



Patented July 6, 1943 MOMENTARILY CONSOLIDATED BOARD PRODUCT William H.Mason, Laurel, Miss., assignor to Masonite Corporation, Laurel, Miss., acorporation of Delaware No Drawing. Application December 10, 1938,

' Serial No. 244,917

4 Claims.

My invention relates to board or sheet products-of ligno-cellulose whichhas been subjected to high temperature and pressure in the presence ofmoisture. Under this treatment the material undergoes hydrolysis and theeasily hydrolyzable components are converted to water-soluble orwater-dispersible compounds, and largely removed, and the balance of thematerial converted to a predominantly plastic state. The new board andother uses, such as for being processed into the denser board referredto below, and is of a specific gravity which is well under 1 but stillquite high, as approximately .7 specific gravity.

The second and preferred board of predominantly plastic ligno-cellulosewhich is embraced within the present invention is a denser board. Thisdenser board may be produced in the same way as the oven-dried boardjust referred to, but in addition it is consolidated. By pre-convertingthe ligno-cellulose into a predominantly plastic condition, it becomespossible to effect permanent consolidation of the board of this materialby making a very short or momentary application of pressure thereto, andthis notwithstanding the pressure is released practically immediatelyafter its application has been completed.

Thus the board can be consolidated rapidly and progressively, as betweenrolls for example, giving a roll-consolidated board with two finishedsurfaces, and the usual platen press can be dispensed with.

The board is immediately ready for use when cooled and preferablyhumidified to contain approximately the normal water content of board,after long time exposure to the atmosphere.

The main objects of the invention are the provision of the boards orsheets referred to above. Furtherobjects will appear from the followingdescription.

In order to put the ligno-cellulose material into such state that it canbe permanently consolidated substantially momentarily by means ofpressure rolls or other means for making substantially momentaryapplication of suflicient pressure, it is first largely converted to apredominantly plastic state by high temperature heat treatment carriedout in the presence of moisture and applied for a time suited to thetemperature used, and to the particular source of ligno-cellulosematerial.

The heat-treated material, preferably after being subdivided andreformed into desired formation, as sheet formation, for example, isdried, and the dry material superheated, and when in the dry,superheated and predominantly plastic state it can be permanentlyconsolidated practically momentarily.

The heattreatment for hydrolyzing is preferably carried out by means ofsteam. When the ligno-cellulose material made use of is Wood,

steam. In order that all parts of the ligno-cellulose material may beheat-treated substantially alike, the Wood is preferably reduced tosmall chips preparatory to the heat treatment, a for instance, chipswhich pass through a one-inch screen.

' Ligno-cellulose material which has been heattreated by means of steamat 350 lbs. pressure v per sq. in. (225 C.) for an unduly long time, is

largely devoid of material in fibrous-appearing state and not welladapted fOr being readily dc watered and felted into sheets, whereawith. a shorter time, preferably about 5 minutes, at this pressure andtemperature, a predominantly plastic ligno-cellulose material isobtained which is well adapted for use in making my new boards. As thepressure and temperature are increased. however, the time at the maximumpressure (after an initial period of pressure rise) can be decreased andrelatively more of the fibrous-appearing ligno-cellulose materialobtained without sacrificing the plasticity characteristics. Forexample, at 600 lbs. per sq. in. (255 0.), the time at full pressure forheat treatment of hard wood, such as gum, can be approximately 45seconds, and for soft wood, such as pine, can be approximately seconds;and at 1000 lbs. per sq. in. (285 'C.), it can be approximately 10seconds for gum to 15 seconds for pine. The time and/or temperature issomewhat less for woody growths, such as corn stalks, cane bagasse,etc., which can be used if desired. These times are subject tomodification by various operating conditions, such as size of gun orother treating apparatus, rate at which the steam is admitted, watercontent of chips, and the like. It is to be noted that in making apredominate conyersion of the ligno-cellulose material into plasticstate as herein described, the time in the gun at full pressure isconsiderably longer than heretofore required for making relativelycoarsefiber for manufacture of fiber boards.

The heat-treated ligno-cellulose material is reduced to a state ofrelatively fine subdivision, permitting reforming into desired shapes,as for example into sheets. The subdivision may be accomplished invarious ways, but is preferably accomplished by carryingon the heattreatment in a closed container or gun such as described in my PatentNo. 1,824,221, and, when the heat treatment has been carried on for thepredetermined period of time, a small outlet is opened whereby theheat-treated material is explosively discharged into a state of relativefineness, and the heat treatment is terminated. The heat treatment maybe carried out in other ways, as in an autoclave, and in such case theheat treatment may be terminated, after a suitable time has elapsed, asby flooding with water, and the material may be reduced to fineness bymeans cellulose constituents have been removed, is not adapted for themaking of the board. Preferably the material taken for treatment is rawwood with the natural encrustants retained, which is the most readilyavailable source of fibrous lignocellulose substance, and contains(together with the cellulose), the lignin and other naturalnoncellulose, i. e., constituents other than cellulose.

I discovered that if the ligno-cellulose material, which has beenrendered predominantly plastic by high temperature heat treatment inpresence of H20, which is considered to effect an action of hydrolysis,is dried completely dry, and further heated, such dry, hot material canbe permanently consolidated'into a dense board or sheet of high specificgravity by application of sufllcient pressure thereto, even though thepressure application is momentary, that is to say applied for a shorttime and released substantially immediately.

' like apparatus, or both, thereby making the final product morewater-resistant.

Sizing materials may be incorporated for fur- I ther enhancing thenaturally high water resistance, as for example 2% of petrolatum orparaflin sizing is useful for this purpose.

The heat-treated and finely divided material, largely freed from thewater solubles, and preferably sized, is preferably formed from waterinto wetlap sheet formation, and excess water removed as by passingthrough squeeze rolls, and the sheet is dried completely dry. The drying(and heating in dry state referred to below) is preferably effected bymeans of heated gases, preferably air with the oxygen largely replacedby products of combustion, inorder to reduce the likelihood of burningat the high temperature made use of. If the operation is interrupted atthis point and the sheets stored temporarily before proceeding withfurther treatment described below, the sheets will absorb moisture. Thismoisture should be dried out before proceeding with the furthertreatment.

As already stated, the dried sheet, which is usually of about .7 sp.gr., can be taken for use asa wallboard if desired, instead of being putthrough the further treatment as hereinafter described.

After the material is dry, it is further heated to over 150 C. andpreferably to over 180 C. Constituents which are converted into gaseousform at such temperature, and might produce blisters during laterapplication of pressure, can be eliminated during such heatingoperation. The sheet after being so dried and heated can be consolidatedby immediate application of sufficient pressure, and the consolidationso effected is permanent, even though the pressure he applied for a veryshort time and then released.

While such pressure application may be made in various ways, the mostconvenient mode consists in passing the sheet through between a pair ofpress rolls forced toward one another at high pressure, as by means ofhydraulic rams.

The rolls are not primarily relied upon to supply heat to the sheetsince the sheet when While the dense board is preferably made fromtreatment.

When using times for heat treatment of the ligno-cellulose material asabove described, especially from about 255 C. to about 285. C., theligno-cellulose material as discharged from the gun appears to largelylose its fibrous structure. With such fibrous material as remains thereis a quantity of quite finely divided material. Both delivered to therolls is at high temperature as above described.

However, the rolls are preferably heated to a temperature which maysomewhat exceed the temperature of the sheets being rolled. In this waythe rolls of steel or the like serve to prevent the sheet from coolingduring the rolling operation, and impart. additional heat at thesurface, giving improved surface qualities.

The rolls are preferably smooth cylindrical rolls, thus making a sheetwhich is finished smooth, preferably on both surfaces. If desired, oneor both-of the roll surfaces may contain patterns which will appear uponthe sheet after rolling.

The roll speed can be varied throughout a fairly wide range, asindicated in the examples given ably formed continuously, and may not beout below. when the holls are heated materially 1 into lengths until ithas passed through the rolls, or it may be cut into desired lengthseither beforeor after the drying and/or heating treatment.

mg a modulus of elasticity dry over 900,000 lbs.

' per square inch, and a modulus of rupture dry over 6,000 1bs..persquare inch. Such board products after being soaked in water for aperiod of 24 hours have a modulus of rupture wet equal to 60% of the drymodulus of rupture, or higher. If the materialis sized, as for examplewith 2% of parafiin during the manufacturing process, the

final product will not absorb water in excess of lo 15% upon 24 hourssoaking in water.

The following table gives representative conditions and the resultsobtained:

Roll speed per min .-.inches 70 150 150 200 300 R 11 diameter d0-- 30 3030 -30 30 Roll pressure "pounds per linear in 3, 260 4, 600 3, 800 4,500 3, 800 R011 temperature 270 225 270 270 270 Sheet drying andsuperheating time minutes.. 25 17 23 23 24 Temperature of superheatedsheets ..U-- 200 225 200 200 20 Specific gravity oi product l. 20 l.22 1. i6 1. l6 1. l4 Modulus oi rupture dry---.pounds per square inch8,300 6, 965 6, 7, 000 7, 365 Modulus of elasticity -.d0. 1,022,000 1,101,000 910,000 962000 022, 500 water absorption in 24 hours .per cent..o. 3 o l B. 9. 3 7. 2 Residual strength (ratio of modulus of ruptureaiter 24 hr. soaking in water to modulus oi rupture dry) per cent 1 88.8 72.8 61. 4

As an illustrative example, gum wood was air dried to about 30% watercontent and\.h0gged into chips. The chips were screened, and thosepassing through a one-inch screen taken for use.

A gun was charged with chips and closed.

Steam was admitted and the pressure raised to 600 lbs. per sq. in. (225C.) and held at this pressure for seconds.

A small outlet was opened and the contents of the gun explosivelydischarged through the open- 1 With the heat-treatment anddisintegration regulated in this way, the resulting relatively finelydivided material was in part fibrous in appearance, with the remainderof finely divided material.

This subdivided ligno-cellulose material was put into water and lightlybeaten in a beater of the Jordan type to make a pulp containing about95% water. It was found that the exploded lignocellulose materialcontained about of water soluble materials, and the water solublecontent was reduced to about 5% by being dissolved out by the water.

The water and fiber mixture was heated above the melting point ofparafiin, and molten paraflin added in an amount about equal to 2% ofdry ligno-cellulcse material by weight, and the paraffin was taken up bythe ligno-cellulose material.

The resulting ligno-cellulose material, representing about 60% of theweight of the chips, was feltedinto sheet form from the water. The stockwas somewhat slow due to its fineness but suificient fibrous materialwas present to permit egress of water and to form felted sheets.

Water was pressed out of the sheet, bringing the water content down toabout 50% (100% on weight of the dry ligno-cellulose material).

The resulting sheets, which were about thick, were dried untilcompletely dry as indicated by the fact that there was no further lossof weight, and were further heated for several minutes with indicationsof evolution of gaseous material. During the drying and further heatingthe shee 5 had shrunk to less than inch in thickness and were about .7sp. gr., and as already stated, could be used for wall boards ifdesired.

These sheets were converted into the board 70 product about /8" thick bypassing same in dry, hot state immediately between hot pressure rolls.The board products thus prepared are quite dense having a specificgravity of about 1 to 1.25. The products are also relatively still andstrong hav- 7 This new board having high dry and wet strength can beused for practically all the purpendent primarily for strength andstifiness upon fiber length and strength of fiber.

Products having the characteristic properties hereinabove described arepreferably made di-'- rectly from the heat-treated ligno-cellulosematerial alone, without incorporation of extraneous bonding or fillerconstituents. However, additions of binders, fillers, pigments and othermaterials, while unnecessary, may be made to the heat-treatedligno-cellulose material and will be embraced within the invention solong as the principles hereof are utilized.

I claim:

1. That improvement in roll-consolidated board products having twofinished surfaces,

which improvement consists in that the board product is composedessentially of extensively hydrolyzed ligno-cellulose material inpredominantly plastic state and containing water solubles fromhydrolysis only in relatively small proportions, and in that the boardproduct is largely without fibrous structure and is principallydependent for strength and stiifness upon the predominantly plasticcharacter of its constituent material rather than upon fiber length orstrength, said board'having a, specific gravity of the ligno-cellulosematerial is wood.

4. Product as claimedin claim '1, and in which the ligno-cellulosematerial is wood, and containing waterproofing material, .said boardhaving a water absorption of less than 15% upon 24 hours soaking.

WILLIAM H. MASON.

